Method of reading optical information and method of recording optical information

ABSTRACT

Exemplary embodiments are provided for recording and reading optical information using holography in which a first recording operation is performed in a first recording region in an overlapping manner by allowing a reference beam and a signal beam with data loaded to interfere with each other in the first recording region, the reference beam being angularly multiplexed at predetermined intervals. And a second recording operation is performed in a second recording region located adjacent to the first recording region or overlapped with the first recording region by allowing the reference beam and the signal beam to interfere with each other in the second recording region, the reference beam being angularly multiplexed between the predetermined intervals.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2007-0139324, filed Dec. 27, 2007, the disclosure of which is herebyincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of reading optical informationand a method of recording optical information, and more particularly, tomethods of reading and recording optical information in a recordingmedium using holography.

2. Description of the Related Art

Recently, as information and computer industries are rapidly beingdeveloped, there is an increasing demand for storage devices that cansatisfy requirements for mass storage capability and high-speed datainput/output. Therefore, a compact disc (CD), a digital versatile disc(DVD), a high definition DVD (HD DVD), a blue-ray disc (BD), aholographic digital data storage (HDDS), and the like are in thelimelight as optical information storage devices capable of storingmassive data and inputting/outputting data at a high speed.

Among various storage devices, a device of processing opticalinformation using a holographic digital information storage, which willhereinafter be referred to as ‘optical information processing device’,records optical information using interference fringes formed bysplitting a beam emitted from a light source into a reference beam and asignal beam, and then allowing the reference beam and the signal beam tointerfere with each other at a recording medium made of a refractivematerial such as a photopolymer. To read optical information, thereference beam input during the recording of the optical informationshould be restored and irradiated to the interference fringes of therecording medium. Thus, a reproducing beam generated by the diffractionat the interference fringe is detected, and the optical information isthen acquired from this reproducing beam.

Meanwhile, the optical information processing device may use variouskinds of multiplexing methods to increase the recording capacity.

Examples of the multiplexing method may include an angular multiplexingmethod, a phase-code multiplexing method, a wavelength multiplexingmethod, a shift multiplexing method, a peristrophic multiplexing method,a correlation multiplexing method, a fractal multiplexing method, and soforth.

In line with the development of multiplexing methods as described above,it is necessary to develop a method of efficiently detecting anddetermining a reproducing beam intended to be reproduced amongreproducing beams generated from recording regions where several bits ofoptical information are recorded in an overlapping manner.

The present invention provides a method of recording optical informationand a method of reading optical information that can easily detect anddetermine a selected reproducing beam intended to be reproduced.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a method of recordingoptical information includes: performing a first recording operation forrecording optical information in a first recording region in anoverlapping manner by allowing a reference beam and a signal beam withdata loaded to interfere with each other in the first recording region,the reference beam being angularly multiplexed at predeterminedintervals; and performing a second recording operation for recordingoptical information in a second recording region adjacent to the firstrecording region in an overlapping manner by allowing the reference beamand the signal beam to interfere with each other in the second recordingregion, the reference beam being angularly multiplexed between thepredetermined intervals.

According to another aspect of the present invention, a method ofreading optical information includes: performing a first reference beamirradiation operation for irradiating a reference beam at a firstmultiplexing angle to a first recording region between the firstrecording region and a second recording region adjacent to the firstrecording region, wherein optical information is recorded in the firstrecording region by the reference beam that is angularly multiplexed atpredetermined angles, and recorded in the second recording region by thereference beam that is angularly multiplexed between the predeterminedangles; and performing a first optical detection operation for detectinga first reproducing beam generated from the first recording region.

In a method of processing optical information according to the presentinvention, optical information can be recorded so as to easily detectand determine a selected reproducing beam, which makes it possible toincrease the reading efficiency of optical information.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a schematic view of an optical information processing deviceaccording to an embodiment of the present invention;

FIG. 2 is a flowchart illustrating a method of recording opticalinformation according to an embodiment of the present invention;

FIG. 3 is a flowchart illustrating a method of reading opticalinformation according to an embodiment of the present invention; and

FIG. 4 is a graph showing intensities of detected reproducing beams thatgenerated by irradiating a reference beam of a first multiplexing angleto recording regions where optical information is recorded through amethod of processing the optical information according to an embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an optical information processing device according to thepresent invention will not be fully described with reference to theaccompanying drawings.

FIG. 1 is a schematic view of an optical information processing deviceaccording to an embodiment of the present invention. Referring to FIG.1, an optical information processing device includes a light source 110,a beam splitter 120, an optical modulator 140, an angle multiplexer 160,and an optical detector 170.

The beam splitter 120 is arranged on an optical path of a beam L emittedfrom the light source 110, and splits the beam L into a reference beam Rand a signal beam S. The beam splitter 120 may include a polarized beamsplitter configured to transmit a portion of the beam L and reflect theother portion of the beam L depending on the polarization of the beam L.The beam L transmitted through the beam splitter 120 may be used as thesignal beam S, and the beam L reflected by the beam splitter 120 may beused as the reference beam R.

Here, a shutter 130 may be provided between the beam splitter 120 andthe optical modulator 140. The shutter 130 controls the progression ofthe signal beam S. That is, the shutter 130 is opened during therecording of optical information to thereby allow the signal beam S tobe incident on the optical modulator 140, whereas the shutter 130 isclosed during the reading of optical information to prevent theprogression of the signal beam S.

The optical modulator 140 is arranged on an optical path of the signalbeam S passing through the shutter 130, and loads data onto the signalbeam S. The optical modulator 140 may employ a spatial light modulatorincluding a plurality of pixels in order to modulate data into a datapage image and load the data page image onto the signal beam S. Thespatial light modulator may include a transmissive spatial lightmodulator such as a twisted nematic liquid crystal (TN-LC), a supertwisted nematic liquid crystal (STN-LC), and a thin film transistorliquid crystal (TFT-LC).

An objective lens 150 may be arranged on an optical path of the signalbeam S onto which data is loaded by the optical modulator 140. Theobjective lens 150 condenses the signal beam S onto a recording mediumM.

The angle multiplexer 160 is arranged on an optical path of thereference beam R, and adjusts an angle of the reference beam R incidenton the recording medium M. The angle multiplexer 160 adjusts the angleof the reference beam R incident on the recording medium M to therebymultiplex the angle of the reference beam R, thus making it possible torecord several bits of optical information within a single recordingregion Sp in an overlapping manner. The angle multiplexer 160 mayinclude a rotating mirror, for example, a Galvano mirror.

The optical detector 170 is arranged on optical paths of reproducingbeams P1 and P2 generated by irradiating the reference beam R onto therecording region Sp of the recording medium M, and detects thereproducing beams P1 and P2. The optical detector 170 may include one ofa charge coupled device (CCD) and a complementary metal-oxidesemiconductor (CMOS) with low power consumption.

An optical filter 180 may be provided between the recording medium M andthe optical detector 170. When the reference beam R is incident on arecording region Sp1 that is intended to be reproduced (hereinafter,referred to as ‘selected recording region’), the optical filter 180transmits the reproducing beam P1 generated from the selected recordingregion Sp1, and blocks the adjacent reproducing beam P2 that may begenerated together with the reproducing beam P1 from a recording regionSp2 adjacent to (or partially overlapped with) the selected recordingregion Sp1 (hereinafter, referred to as ‘adjacent recording region’).The optical filter 180 may include a polytopic filter.

For convenience in description and understanding, it is assumed that theselected recording region Sp is a first recording region, and theselected reproducing beam P1 is a first reproducing beam, and likereference numerals are given to both of them. Likewise, it is assumedthat the adjacent recording region Sp2 is a second recording region andthe adjacent reproducing beam P2 is a second reproducing beam, and likereference numerals are also given to both of them.

Herebelow, a method of processing optical information according to anembodiment of the present invention will be described in detail withreference to the accompanying drawings.

FIG. 2 is a flowchart illustrating a method of recording opticalinformation according to an embodiment of the present invention.Referring to FIGS. 1 and 2, the beam L is emitted from the light source110 so as to record optical information. The beam L is split into thereference beam R and the signal beam S by the optical splitter 120.

The signal beam S is transmitted through the beam splitter 120, and thereference beam R is reflected by the beam splitter 120. The signal beamS transmitted through the beam splitter 120 progresses toward theoptical modulator 140 after passing through the shutter 130. Data isloaded onto the signal beam S by the optical modulator 140, and thesignal beam S with the data loaded is condensed onto the recordingmedium M by the objective lens 150.

The reference beam R reflected by the beam splitter 120 is angularlymultiplexed by the angle multiplexer 160, and irradiated onto therecording medium M. The reference beam R and the signal beam S interferewith each other at the recording region Sp of the recording medium M toform interference fringes, and thus optical information is recorded.

In operation S11, the reference beam R is incident on the recordingmedium M at one of first multiplexing angles that is angularlymultiplexed. and interferes with the signal beam S in the firstrecording region Sp1. Here, the first multiplexing angles havepredetermined intervals therebetween. Also, in operation S13, thereference beam R is incident on the recording medium M at one of secondmultiplexing angle that is angularly multiplexed and interferes with thesignal beam S in the second recording region Sp2 adjacent to (orpartially overlapped with) the first recording region Sp1. Here, thesecond multiplexing angles are different from the first multiplexingangles and also have predetermined intervals therebeween. And,preferably, the second multiplexing angles could be between the firstmultiplexing angles, respectively.

To facilitate the understanding, for example, the reference beam Rirradiated onto the first recording region Sp1 may have the firstmultiplexing angles such as 1°, 2°, 3°, . . . , n−1°, and n°, and thereference beam R irradiated onto the second recording region Sp2 mayhave the second multiplexing angles such as 1.5°, 2.5°, 3.5°, . . . ,(n−1)+0.5°, and n+0.5°.

As for the first and second multiplexing angles, each of the first andsecond multiplexing angles has an equal interval of 1°. Furthermore, thefirst and second multiplexing angles do not overlap each other. And,preferably, the second multiplexing angles are median values of pairs ofadjacent first multiplexing angles, respectively.

Hence, the reference beam R, which has the first and second multiplexingangles having an equal interval and not overlapping each other,interferes with the signal beam S in the first and second recordingregions Sp1 and Sp2 to thereby form interference fringes.

That is, n number of bits of optical information can be recorded in eachof the first and second recording regions Sp1 and Sp2 in an overlappingmanner by irradiating the reference beam R having the first and secondmultiplexing angles onto the first and second recording regions Sp1 andSp2, respectively.

FIG. 3 is a flowchart illustrating a method of reading opticalinformation according to an embodiment of the present invention.Referring to FIGS. 1 and 3, the beam L is emitted from the light source110 to read optical information. The beam L is split into the referencebeam R and the signal beam S by the beam splitter 120.

The signal beam S is transmitted through the beam splitter 120, and thereference beam R is reflected by the beam splitter 120. The signal beamS transmitted through the beam splitter 120 is blocked by the shutter130.

Meanwhile, the reference beam R reflected by the beam splitter 120 isangularly multiplexed by the angle multiplexer 160, and then incident onthe recording medium M. At this time, in operation S31, the referencebeam R is incident on the recording medium M at one of the firstmultiplexing angles, allowing the first reproducing beam P1 to begenerated from the first recording region Sp1.

Herein, the reference beam R may be irradiated to the second recordingregion Sp2 according to the beam width of the reference beam R when thereference beam R is irradiated to the first recording region Sp1.Accordingly, the first reproducing beam P1 and the second reproducingbeam P2 may be generated together in the first and second recordingregions Sp1 and Sp2. The optical filter 180 blocks the secondreproducing beam P2 progressing toward the optical detector 170, andallows only the first reproducing beam P1 to progress toward the opticaldetector 170. The second reproducing beam P2 passing through the opticalfilter 180 is detected by the optical detector 170.

Even though the optical filter 180 blocks the second reproducing beamP2, the first reproducing beam P1 and the second reproducing beam P2 aregenerated in front of the optical filter 180 in an overlapping manner.In this case, therefore, a mixed beam may progress toward the opticaldetector 170. Accordingly, in operation S33, the first reproducing beamP1 and the second reproducing beam P2 may be detected together by theoptical detector 170.

Consequently, in operation S37, the first reproducing beam P1 isdetermined using intensities of the reproducing beams P1 and P2 detectedby the optical detector 170. Therefore, in operation S37, opticalinformation can be acquired.

To facilitate the understanding, following description will be made bycomparing the intensities of the first and second reproducing beams P1and P2 with each other depending on the reference beam R of the firstmultiplexing angle according to the aforesaid embodiment.

FIG. 4 is a graph showing intensities of detected reproducing beamsgenerated by irradiating the reference beam of the first multiplexingangle to recording regions where optical information is recorded throughthe method of processing the optical information according to anembodiment of the present invention. Referring to FIG. 4, the referencebeam R having the first multiplexing angle such as 1°, 2°, 3°, . . . ,n−1°, and n° interferes with the signal beam S, as illustrated in theforegoing embodiment. Therefore, the reference beam R is irradiated tothe first recording region Sp1 at an angle such as 1°, 2°, 3°, . . . ,n−1°, and n° so as to generate the first reproducing beam P1 in thefirst recording region Sp1.

The first reproducing beam P1 generated by irradiating the referencebeam R having the first multiplexing angle to the first recording regionSp1 is detected by the optical detector 170, and has the highest lightintensity at angle of 1°, 2°, 3°, . . . , n−1°, and n°.

On the contrary, when the reference beam R having the first multiplexingangle is irradiated to the second recording region Sp2 where thereference beam R having the second multiplexing angle such as 1.5°,2.5°, 3.55°, . . . , (n−1)+0.5°, and n+0.5 interferes with the signalbeam S, the second reproducing beam P2 detected by the optical detector170 has the lowest light intensity at an angle of 1°, 2°, 3°, . . . ,n−1°, and n°.

Therefore, the reproducing beam having higher light intensity may bedetermined as the first reproducing beam P1 by comparing lightintensities of the two reproducing beams P1 and P2 detected by theoptical detector 170, thus acquiring optical information from the firstreproducing beam P1.

So far, the description has been made assuming that the selectedrecording region Sp1 is the first recording region, and the selectedreproducing beam P1 is the first reproducing beam. However, when thereference beam R is irradiated to the second recording region at thesecond multiplexing angle even assuming that the selected recordingregion Sp1 is the second recording region and the selected reproducingbeam P1 is the second reproducing beam, operation and function aresimilar to the aforesaid case. Here, the first recording region may bethe adjacent recording region Sp2, and the first reproducing beam may bethe adjacent reproducing beam P2.

Consequently, the method of processing optical information according tothe present invention makes it possible to easily determine the selectedreproducing beam P1 from the adjacent reproducing beam P2 even thoughthe selected reproducing beam P1 and the adjacent reproducing beam P2are generated in an overlapping manner.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims. Thus, itwill be apparent to those having ordinary skill in the art that suchchanges and modifications fall within the protected scope of the presentinvention.

1. A method of reading optical information, the method comprising:performing a first reference beam irradiation operation for irradiatinga reference beam at one of first multiplexing angles to a firstrecording region, wherein optical information is recorded in the firstrecording region by the reference beam that is angularly multiplexed atthe first multiplexing angles, and recorded in the second recordingregion by the reference beam that is angularly multiplexed to a secondmultiplexing angles which are between the first multiplexing angles,respectively, and wherein the second recording region is locatedadjacent to the first recording region or partially overlapped with thefirst recording region; and performing a first optical detectionoperation for detecting a first reproducing beam generated from thefirst recording region, wherein the first optical detection operationfurther performs detecting a second reproducing beam overlapping thefirst reproducing beam generated by irradiating the reference beam atthe one of the first multiplexing angles to the second recording region,wherein the first optical detection operation further comprises a firstoptical determination operation for determining the first reproducingbeam from the first and second reproducing beams overlapping each other,wherein the first optical determination operation comprises comparinglight intensities of the first and second reproducing beams with eachother, and determining the reproducing beam with a higher intensitybetween the first and second reproducing beams as the first reproducingbeam.